Embodiments relate to a semiconductor device. Some embodiments relate to a method of fabricating a CMOS image sensor.
Image sensors may refer to semiconductor devices which may change an optical image into an electric signal. Image sensors may be categorized as a Charge Coupled Device (CCD) image sensor and/or a Complementary Metal-Oxide-Silicon (CMOS) image sensor. An image sensor may include a pixel region having photodiodes to sense light, and/or a logic region to process sensed light into an electric signal to obtain optical data. An image sensor may refer to a device which receives light incident on and/or over a pixel region which may capture an image using photodiodes of respective pixels and/or at least one transistor.
Referring to FIG. 1, a layout 100 of a unit pixel of an image sensor may have a 4-TR structure. A unit pixel of an image sensor may include a photodiode region 110, a transfer transistor (Tx) 115, a floating diffusion region 120, a reset transistor 125, a drive transistor 130, a select transistor 140, and/or a plurality of metal contacts 117, 124, 127, 132, 142, and/or 150. A plurality of metal contacts 117, 124, 127, 132, 142, and/or 150 may be connected to an active region and/or gate electrodes of transistors.
A metal contact etching process, which may be one processes used to fabricate an image sensor, may be performed simultaneously on and/or over a pixel region and a logic region that may be in common. It is important to form a contact while reducing damage to photodiodes due to etching in a metal contact etching process. Damage to a silicon surface on and/or over a pixel region of an image sensor, which may be sensitive to a dark current property, may result from a metal contact etching process and may need to be minimized.
An etching depth may be relatively increased to assure an etching margin to form contact holes on and/or over a logic region. However, an etching depth to contact holes on and/or over a pixel region may be relatively increased. Therefore, photodiodes including a floating diffusion region may be damaged, and/or leakage current may be maximized. A dark current property may be minimized. On the other hand, when an etching margin to the contact holes on and/or over a logic region may be relatively reduced to prevent damage to a pixel region due to etching, contacts on and/or over a logic region having many circuits may not be properly formed.
Accordingly, there is an need for an image sensor and a method of manufacturing an image sensor which may substantially prevents a pixel region from being damaged by an etching process to form contact holes. There is a need for an image sensor and a method of manufacturing an image sensor which may maximize a dark current property and/or secures a yield.